So I am curious about the possibility of making custom torque boxes and wanted feedback or if anyone else has done this.
I have had my new floor, cowls, and rail work done and it is nice and clean with no torque boxes installed yet. I was thinking about making a torque box, well not really a box, but using tube steel or square steel stock and welding together a custom made frame that will go in place of a torque box but would be welded in all the same stress points. I just think it would be cleaner, no chance of future rusting out, and stronger.
I like the idea. I will eventually need to replace the passenger side on my 68 and was wondering the same thing. I visualize something like a capital letter “H” (or a tie fighter without the cockpit bubble), where the legs of the H (or solar panel parts) are flat rectangular plates that get welded to the rocker panel and floor support and the horizontal part is some strong 2" or so tubing. I’d add some gussets to where the tubing attaches to the legs to further prevent twisting.
From an engineering standpoint the structure is triangulated through the flat metal plate and the triangular gussets at the ends. The Ford engineers knew what they were doing. IF you use the two plates with the tube in between you are not addressing the right forces. The tube structure would be very strong from a side impact, but would do little to control the twisting forces that the torque box is there to control.
When you look at a flat rectangular plate, what you need to visualize, from a structural integrity standpoint, is a set of triangles. The hypotenuse is created by an imaginary line connecting the opposite corners. If you took Yorgle’s drawing and made the gussets as large as possible they would extend from the bottom of one leg to the top of the other. Put two together, and you get a flat rectangular plate. This takes care of forces in the horizontal plane, but you also have force in the vertical" you don’t what the sub-frame to be able to rotate relative to the body. This is where the triangular end plates come into play. By connecting the end plates to the flat plate and the floor, creating a wedge shaped box, you are really adding strength in both planes.
I agree, but the Ford engineers were limited to using stamped sheet metal, in which the only way to create a rigid structure is by making a box. I expect that all (or even more) rigidity of the original torque box could be created in other shapes using thicker and stronger materials, such as plates and tubing.
I have seen somthing like this done on 65-66 mustang/shelby race cars. I think they used 2" x 3" rectangle with te ends cut at an angle to tie the brace in closer to the suspension on the frame rail. Mike